Annular fluid containment device

ABSTRACT

An annular fluid containment device comprises one or more fluid seals disposed on a section of production string tubing, and a vent tubing extending along the section of production tubing from below the fluid seals to above the fluid seals. The fluid seals are sealed against the vent tubing and the production tubing, and configured to form a seal within an annular space between the production tubing and a well casing, with the vent tubing providing venting for pressure equalization between the annular space below the fluid containment device and the annular space above the fluid containment device. The fluid containment device placed in a production string below a leak in the casing prevents unwanted fluid from entering the production zone. An additional tubing may be provided similarly to the vent tubing to allow introduction of a fluid into the well below the fluid containment device.

FIELD OF THE INVENTION

The present invention relates to apparatus for repairing a damaged well casing, and more particularly to a method and apparatus for inexpensively repairing a producing well.

BACKGROUND

In the well servicing industry, a common problem encountered is a damaged well casing in a marginally producing well. It is desirable to quickly and inexpensively repair a damaged well casing in a marginally producing well, such that the well may be maintained in production in a cost effective manner.

In a typical gas or oil well, for example, a well casing is placed within a bore hole such that the well casing extends from the surface to the production zone. A production tubing string is placed within the casing, and the gas or oil is withdrawn through the production string. An annular space surrounds the production string, between the exterior wall of the production string and the interior wall of the well casing. During the life of the well, the casing may become corroded, resulting in holes or openings in the casing which allow water or other undesirable fluids to enter into the annular space between the production string and well casing, and travel downward to reach the production zone. Accumulation of the undesirable fluids within the annular space may result in reduced production, either by inhibiting the free flow of gas or oil into the production zone and into the production tubing, or simply by displacing a substantial quantity of the gas or oil such that pumping operations must pump a large quantity of the undesirable fluid, reducing the efficiency of recovery of the gas or oil.

For example, the well casing may pass through a water-bearing sand formation well above an oil formation from which oil is pumped. Corrosion of the well casing such as by the water in the water-bearing sand formation may result in holes, cracks or other openings in the well casing, allowing entry of the water into the well casing. Once entered into the annular space within the well casing, the water will travel to the bottom of the well to the oil formation. Accumulation of excessive water may result in hydrostatic pressure sufficient to prevent entry of oil into the casing, or may simply mix with oil such that a diminished quantity of oil is recovered as the water is pumped up along with the oil. In either case, it is desirable to prevent water, or other undesirable fluids, from reaching the production zone.

It is therefore desirable to introduce a sealing device into the annular space, below the damaged portion of the casing and above the production zone. However, introduction of a sealing device into the annular space may result in another problem, in that pressure from the oil formation may build up to a point wherein, because of the pressure build up, the well stops producing. That is, as pressure within the casing or the annular space between the casing and the production string increases, the tendency for oil to flow into the casing decreases. Therefore, it is desirable, in a sealing device provided in the annular space as discussed above, to include a venting means for venting and releasing pressure through the sealing device, while preventing water, or other undesirable fluids, from reaching the production zone.

SUMMARY

An annular fluid containment device and method are provided for introducing a seal into the annular space between a well casing and a production tubing string within the casing, and providing a venting means for venting and releasing pressure through the seal.

According to one aspect of the invention, an annular fluid containment device comprises a production tubing having an outside diameter configured for placement within a well casing to define an annular space between an outside wall of the tubing and an inside wall of the well casing. At least one generally cylindrical fluid seal is disposed on the production tubing, the fluid seal having upper and lower collar portions and an annularly protruding central sealing portion. The at least one generally cylindrical fluid seal is disposed about the length of tubing. A vent tubing extends from below the at least one generally cylindrical fluid seal to above the at least one generally cylindrical fluid seal, providing venting and pressure equalization between an annular space below the fluid containment device and an annular space above the fluid containment device.

According to another aspect of the invention, a channel is defined between the fluid seal and the production string for accommodation of the vent tubing.

According to a further aspect of the invention, the annular fluid containment device may be additionally provided with a means for conveying a fluid into the well. For example, it may be desirable to introduce a deposit inhibitor or other fluid, for example such as a paraffin inhibiting agent, into the well below the annular fluid containment device, for treatment of the well.

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an annular fluid containment device.

FIG. 2 is cross-section view of an annular fluid containment device.

FIG. 3 is a diagrammatic view showing placement of an annular fluid containment device within a well casing.

FIG. 4 is an end view of an annular fluid containment device showing an arrangement of a vent tubing of the annular fluid containment device.

FIG. 5 is an end view of an annular fluid containment device showing an alternative arrangement of a vent tubing of the annular fluid containment device.

FIG. 6 is a side view of another embodiment of an annular fluid containment device.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The annular fluid containment device 100 is formed by placing one or more fluid seals 110 about a section of production tubing 104, and extending a length of vent tubing 106 from below a lower-most of the fluid seals 110 to above an upper-most of the fluid seals 110. In one embodiment, the vent tubing 106 is disposed along the production tubing section 104, and the fluid seals 110 are disposed over both the vent tubing 106 and the production tubing section 104, such that the vent tubing 106 is disposed between the fluid seals 110 and the outer surface of the production tubing 104. The fluid seals 110 are sealed against the vent tubing 106 and the production tubing 104, such as by providing a rubber cement or sealant or the like to fix the fluid seals 110 to the production tubing section 104 and form a seal.

The fluid seals 110 are generally cylindrical members having upper and lower collar portions 112 and a central, annularly protruding sealing portion 114. The fluid seals 110 may be made of a resilient, elastic material such as rubber to form a good fluid seal against the inner wall of the well casing 200, when the annular fluid containment device 100 is placed within the well casing 200. As the fluid seals 110 are placed onto the production tubing section 104, they may be somewhat compressed lengthwise in order to cause further protrusion of the annularly protruding sealing portion 114. It is desired that the annularly protruding sealing portion 114 of the fluid seals 110 have, once placed on the production tubing section 104, an outer diameter slightly greater than the inside diameter of the well casing, so that a secure seal is formed by the fluid seals 110 against the inside wall 202 of the well casing 200 once the annular fluid containment device 100 is placed. For example, if the annular fluid containment device 100 is to be placed within a 5½ inch casing (having a 5 inch inner diameter), the fluid seals 110 may be configured so that the outside diameter of the annularly protruding sealing portions 114 is about 5½ inches, slightly greater than the inner diameter of the well casing 200. These example dimensions are not intended to be limiting, and it can be understood that variation in the dimensions of the outside diameter of the annularly protruding sealing portions 114 with respect to the inside diameter of the well casing 200 may be varied in view of factors such as the degree of seal desired or required, or the degree of ease or difficulty in placing the annular fluid containment device 100 within the well casing 200.

While the fluid seals 110 may be placed onto the production tubing 102 and over the vent tubing 106 by simply stretching the collar portions 112 over the production tubing 102 and vent tubing 106, it is preferable to provide accommodation for the vent tubing 106 between the fluid seals 110 and production tubing 102 without deformation of the fluid seals 110, since a better seal may be achieved. Referring to FIG. (TBD), positioning the vent tubing 106 between the fluid seals 110 and the production tubing 102 can be facilitated by providing a sleeve 118 between the fluid seals 110 and the production tubing 102, wherein a channel 120 is formed in the sleeve 118 to accommodate the vent tubing 106 without distortion of the fluid seals 110. Such an arrangement results in a good seal between the fluid seals 110 and the production tubing 102, since distortion of the fluid seals 110, which may make sealing of the fluid seals against the production tubing 102 difficult, is eliminated.

Alternatively, referring to FIG. (TBD), a channel 122 may be defined in the inner wall surface 124 of the fluid seals 110 themselves to accommodate the vent tubing 106 between the fluid seals 110 and the production tubing 102. Again, such an arrangement contributes to good sealing of the fluid seals 110 against the production tubing 102.

Once placed onto the production tubing 104, each of the fluid seals 110 may be further fixed in place by straps or bands 126 which may be disposed at each end of each of the upper and lower collar portions 112 of the fluid seals 100. For example, the straps or bands 126 may be steel clamping straps or the like. Additionally, a sealing material or adhesive 128, such as a silicone sealant, rubber cement or other material may be provided between the collar portions 112 and the production tubing 104, surrounding the vent tubing 106 or elsewhere as needed such that the annular fluid containment device 100 forms a fluid tight seal when placed into the well casing 200.

Referring to FIG. 6, an exemplary placement of an annular fluid containment device 100 is shown. In practice, the annular fluid containment device 100 may be placed within the well casing 200 by removing a length of the production string from the casing, corresponding generally to the depth of the damaged casing. The annular fluid containment device 100 (generally, a production tubing section 102 fitted with the fluid seals 100 and vent tubing 106 as described herein) is inserted into the production string, and the production string replaced into the casing such that the annular fluid containment device is located below the damaged casing. For example, if the casing is damaged at a depth of about 1200 feet, a length of about 1250 feet of the production string may be removed, and the annular fluid containment device inserted into the production string to correspond generally to a depth of about 1250 feet, placing the annular fluid containment device below the damaged portion of the casing.

Once the annular fluid containment device 100 is placed and positioned in the well, the vent tubing 106 is preferably extended from below the fluid seals 100 to the surface, or to a point above the anticipated static level of the unwanted fluid, so that the unwanted fluid does not enter the well production zone below the annular fluid containment device 100 through the vent tubing 106.

In another embodiment, referring to FIG. 5, a second tubing, usable as a fluid delivery tubing 116 may be provided in a like manner to the vent tubing 106. In practice, the fluid delivery tubing 116 may be used to deliver a fluid, for example such as a deposit inhibitor or other well treatment fluid, into the well below the annular containment device 100. Such a fluid delivery tubing 116 typically will be extended to the surface, for introduction of the fluid.

It will be understood that the above-described embodiments of the invention are illustrative in nature, and that modifications thereof may occur to those skilled in the art. Accordingly, this invention is not to be regarded as limited to the embodiments disclosed herein, but is to be limited only as defined in the appended claims. 

1. An annular fluid containment device, comprising: a production tubing having an outside diameter configured for placement within a well casing to define an annular space between an outside wall of the tubing and an inside wall of the well casing; at least one generally cylindrical fluid seal, having upper and lower collar portions and an annularly protruding central sealing portion, the at least one generally cylindrical fluid seal being disposed about the length of tubing; and a vent tubing extending from below said at least one generally cylindrical fluid seal to above said at least one generally cylindrical fluid seal.
 2. The annular fluid containment device of claim 1, wherein said vent tubing is disposed along said production tubing between said fluid seal and said production tubing.
 3. The annular fluid containment device of claim 1, wherein a channel is defined in an inner wall of said fluid seal, said vent tubing being disposed along said production tubing within said channel.
 4. The annular fluid containment device of claim 1, further comprising a sleeve disposed between said fluid seal and said production tubing.
 5. The annular fluid containment device of claim 4, wherein a channel is defined in said sleeve, said vent tubing being disposed within said channel.
 6. The annular fluid containment device of claim 1, further comprising a sealing material applied between said fluid seal and said production tubing.
 7. The annular fluid containment device of claim 1, further comprising a clamping strap disposed about each of the upper and lower collar portions of said fluid seal. 